Blackberries (species in the genus Rubus) are uniquely suited to vegetative propagation, offering an economical way to increase your garden’s yield without the genetic variability that comes with seeds. Growing new plants from cuttings is a highly effective method because blackberries naturally produce canes capable of developing adventitious roots when conditions are favorable. This technique allows you to quickly multiply a desirable cultivar, ensuring the new plants are genetically identical to the parent, which is a significant advantage. The process relies on manipulating the cane’s natural growth cycle to encourage root formation before new leaf growth.
Selecting and Preparing Cutting Material
Timing is the most important factor when choosing material, as the approach differs significantly depending on the season. Hardwood cuttings are taken during the dormant season (late fall through early spring) from the previous year’s growth. These canes should be woody, mature, and roughly the diameter of a pencil, offering a robust, long-term approach to propagation. Softwood cuttings are harvested during the active growing season (late spring or early summer) from the current year’s new, pliable growth, often called primocanes.
Regardless of the type, selecting healthy, disease-free canes is paramount to ensure the success of the resulting plants. Hardwood sections should be 6 to 8 inches long, cut using sharp, sterilized pruners to prevent disease transmission. To orient the cane for planting, make a straight cut at the top, just above a node, and a slanted cut at the bottom end, which is inserted into the rooting medium.
Softwood cuttings are shorter, around 4 to 6 inches, and must retain a few upper leaves for photosynthesis. Before planting, carefully remove the lower leaves to prevent rotting and pathogen introduction in the moist medium. The remaining upper leaves are sometimes trimmed in half to reduce the surface area, minimizing water loss while the cutting develops roots.
Step-by-Step Rooting Techniques
The rooting medium must be sterile and well-draining to prevent fungal diseases and root rot, which are common issues during this phase. A mix of materials like peat moss, coarse sand, perlite, or vermiculite provides the necessary aeration and moisture retention. Hardwood cuttings, taken while dormant, often do not require rooting hormone but benefit from its use, as it contains auxins that stimulate root formation.
Hardwood Rooting
Insert the prepared hardwood canes into the medium, ensuring the lower angled cut is completely buried and at least two nodes are below the soil line. Keep the container in a cool, sheltered location where the temperature remains stable. This allows the base to callus and form roots slowly over the winter or early spring. The medium must be kept lightly moist, not saturated, throughout this period to encourage root growth without rotting the cane.
Softwood Rooting
Softwood cuttings require a different, more tender environment to survive and root successfully. After dipping the base in rooting hormone, place them into the sterile medium. The primary requirement is high humidity to compensate for the lack of a developed root system. Achieve this by covering the container with a clear plastic bag or dome to create a miniature greenhouse effect, placing it in bright but indirect sunlight. Keep the medium and surrounding air consistently moist through regular misting; root development often occurs within three to four weeks.
Caring for Rooted Cuttings and Transplanting
The most reliable sign that a cutting has successfully rooted is the appearance of new leaf growth at the top of the cane. This new growth indicates the plant has established a functional root system capable of supplying water and nutrients to the developing foliage. While a gentle tug will reveal resistance if roots have formed, avoid disturbing the fragile new root ball.
Before moving the rooted cuttings outdoors, they must undergo a process called hardening off. This involves gradually acclimating the young plants to the harsher outdoor conditions, including direct sunlight, wind, and fluctuating temperatures. Initially, place the plants in a sheltered, shaded area for a few hours daily, slowly increasing the duration and exposure over a period of one to two weeks.
The best time to transplant is in late spring or early summer after the last expected frost, or in the fall during the next dormant season. When transplanting, the soil in the garden bed should be well-prepared, ideally with a slightly acidic pH between 5.5 and 7.0, and amended to ensure excellent drainage. Set the young plant into the ground at the same depth it was growing in the container. Initial care involves ensuring the top inch of soil remains consistently moist for the first few weeks, followed by a regular watering schedule of one to two inches per week, especially during dry spells, to support the establishment of the new root system.